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"J " ""'" foe" ~ ...:t NPDIlS Permit No. CO-0042161 Sa1ini~ Control Study Twentymile Coal Company 5.0 Conclusions and Recommendatious This S#inity Control Study was prepared to comply with the Regulations foc Implementation of the ;Colorado River Salinity Standards through the NPDES Permit Program. These' regulatipns require that treatment options be examined if a permit holder's discharge of salts ' into a tHbutary of the Colorado River exceeds I ton/day or 350 tons per year. This study focusedlon determining the feasibility, cost and effectiveness of three alternatives for reducing' or eliminating the salt loading to Fish Creek from the discharge outfall 00 I covered under ' ' Twenl}1iuleCoal Company's (fCC) current NPDES Permit CO-0042161. Outfall 001 dischl!rges from a ~edimentation pond which treats water from underground mine operations via the Fish Creek Bbrehole. ;z The analysis involved characterizing the current flows, IDS concentrations, and salt loading in Fish Cr~k both upstream and downstream of the discharge outfall. These "baseline" conditio!).s were established using flow, IDS and specific conductance monitoring records, from th~last four and one half years (April, 1990 through September; 1994) for the discharge outfall, and for Fish Creek above and below the discharge. Baseline i conditions on Fish Creek downstream of the discharge were compared with . the estimate4 effects of three alternatives to reduce salt loading from the discharge. These a1ternati~es were complete salt elimination by deep well injection (Option 1), partial salt removal illy reverse osmosis (Option 2), and partial salt reduction by deep well injection. (Option 3). 5.1 Qption 1 Option I,' complete discharge elimination, results in the greatest reduction in salt loading, The average 4aily salt load at the discharge outfall is estimated to be 1.83 tons/day for the 1990-1994 record, Complete elimination of the discharge would reduCe salt load in Fish Creek,' , by 14 to ~O percent. Average IDS concentration downstream from the discharge outfall would decline fr~m 781 ppm to 463 ppm. The depletion of streamflow by deep well injection may require a ~urface water right, which might be difficult to obtain if water depletion results in material d>unage to the quantity of water supplying a designated Alluvial V alley Floor , The reduction~ in salt loads and IDS concentrations in Fish Creek would not be measurable at high flows, but, would be significant during low flow. The capital cost of Option I is $4,793,000 with annual operating costs of $106,000. The const1')Jction of this option is technically feasible, although it is uncertain whether injection well permits could be obtained and whether the Dakota Sandstone would prove suitable for_ injection, ;;, AHA Filename: \4SALCN1.DOC Page 32 J 1:59 AM 09129/95 """"'------"- __ ~_ _ .'-_~ -'" '.L A~~ fl~